Convert GRID_DIALOG to .ui

Change-Id: I4476559cc2e6a90b65d5bdc8169b256929f07f7e
Reviewed-on: https://gerrit.libreoffice.org/9734
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>